This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our studies in the past have focused on the short term effects of exercise and amino acids in sedentary subjects. We would like to expand our research to include recreationally active middle aged people looking at the effect of essential amino acid on muscle growth. We hypothesize that long-term nutritional supplementation with essential amino acids will grow muscle and increase strength in healthy, trained middle-aged people. We will determine if long-term nutritional supplementation with essential amino acids can grow muscle and increase strength in healthy, trained middle aged people. Enrolled subjects will be randomized to receive supplement or a placebo (i.e. like a sugar pill ) every day for one year. They will be tested every four months to check for muscle growth, strength testing, and safety of the supplements. At the end of the year all tests will be performed again to get the final results. This pilot study will serve to determine feasibility and safety of a nutritional intervention for muscle growth in trained middle-aged persons, and will allow us to collect preliminary data for a larger clinical trial to determine the optimal dose and composition of nutritional supplements for the prevention of muscle weakness and loss with aging.